Ultrastructural Evaluation of Parathyroid Glands from Bulls with Ultimobranchial Thyroid Tumors

A syndrome of ultimobranchial thyroid tumors (UTT) of aged bulls shares many characteristics with medullary thyroid carcinoma in man (Black et al. Cancer 32:867-878, 1973). Multiple endocrine tumors (pheochromocytomas, pituitary adenomas) and severe skeletal disease (vertebral osteosclerosis with ankylosing spondylosis and degenerative osteoarthrosis) often are detected coincidentally in bulls with UTT. Parathyroid hyperplasia or chief cell adenomas have been reported to occur frequently in humans with familial medullary thyroid carcinoma. However, parathyroid gland activity in bulls with UTT has not been well characterized. The objectives of this investigation were: (1) to investigate the histopathologic and ultrastructural alterations in parathyroid glands of bulls with UTT compared to control bulls of the same age range without C-cell tumors, and (2) to correlate these morphologic findings in the parathyroids with changes in serum calcium, phosphorus, and immunoreactive parathyroid hormone.